Herein we report the eco-friendly and catalyst-free single step synthesis of solid carbon spheres, 1-10 mu m in diameter, using vegetable oils derived from different bio-resources as the carbon source. The surface functionality of the synthesized carbon spheres was examined by Fourier transform infrared and charge polarized magic angle spinning nuclear magnetic resonance spectroscopy. The resulting carbon spheres were 100% pure, i.e. free of metal impurities, carbon soot and other structures; and do not require post treatments, such as extraction and purification. A detailed study showed that the synthesis of the carbon spheres proceeds through the formation and self-condensation of aromatic hydrocarbons generated from the oil precursor under autogenic pressure. The carbon spheres were used further as a template for the synthesis of nano crystalline ZnO and MgO hollow spheres.